Continuous rotary filter



g' y N43 H. w. DENHARD ET AL I 2,446,746

- CONTINUOUS ROTARY FILTER Original Filed Dec. 11, 1943 2 Sheets-Sheet lINVENTOR HARRY. w DENHHZD FRANK w- BEITTH/N ATTORNEYS 5 1948- H. w.DENHARDEF AL. 2,446,746

CONTINUOUS ROTARY FILTER Original Filed Dec. 11, 1943 2 Sheets-Sheet 2jlg 5 INVENTOR5 HARE DENHHED F EHNK B2! TTH/N HNTHON SEEP .5

z 7 BY ATTORNEYS Patented Aug. 10, 1948 CONTINUOUS ROTARY FILTER HarryW. Denhard, Sebastopol, Frank W. Brit- -tain, Piedmont, and Anthony G.Serpas, Oakland, Calm, assignors to Oliver United Filters Incorporated,Oakland, Calif., a corporation of Nevada Continuation of applicationSerial No. 518,958, December 11, 1943. This application February 16,1948, Serial No. 8,673

3 Claims. (Cl. 210-201) This invention relates in general to continuousrotary filters, and more particularly to a scroll discharge fordischarging the cake formed and carried on such filters, and thisapplication is a continuation of our application Serial No. 513,958filed December 11, 1943, for" "Continuous rotary drum filters, nowabandoned.

There are now in current use various types of discharging devices suchas doctors or scrapers;

- couch rolls; discharge rolls such as exemplified in the GardellaPatent No. 1,812,648; vacuum dischargers such as exemplified in'theHillier Patent No. 1,914,742; and the Hydrair discharger such asexemplified in the Young Patent No. 2,070,074. While each of these typesof dischargers is effective in discharging certain types of cakes, noneof them is effective in discharging relatively thin,

low density cakes such as are sometimes encountered in filtering groundwood paper pulp.

In general, the object of this invention is the provision of a scrolldischarger, particularly designed for discharging relatively thin, lowdensity a roll mounted across the face and immediately adjacent to thedrum of the filter, for rotation in the same clockwise direction as thefilter drum, in combination with a screw conveyor or discharge scrollmounted over the drum and to the rear of the discharge roll, forrotation also in the same clockwise direction as the filter drum, thefunction of the discharge roll being to cause the cake or sheet carriedon the filter drum continuously to roll up upon itself, and the functionof the screw conveyor or discharge scroll being continuously to take acut from the roll of solids and continuously to advance said outlaterally to one or both ends of the filter drum.

A further object of the invention is the provision of means fordelivering a fluid current between the filter drum and the dischargeroll, for the purpose of aiding the discharge rollin causing the cake toroll up upon itself and for controlling the density of the cake at thispoint.

The invention possesses other advantageous selected for illustration inthe drawings accom- 4.

panying and forming a part of the present specificationis outlined infull. In said drawings, one form of the invention is shown, but it is tobe understood that it is not limited to such form, since the inventionas set forth in the claims may be embodied in a plurality of forms.

Referring to the drawings: Fig. 1 is an elevation of the valve end of acon tinuous rotary drum filter embodying the objects of our invention.

Fig. 2 is a side elevation of the filter shown in Fig. 1.

Fig. 3 is an enlarged section taken on the line 3-3 of Fig. 2,diagrammatically illustrating the discharge mechanism constituting theobjects of our invention.

Fig. 4 is an enlarged section taken on the line 4-4 of Fig. 3, showingthe operation of the screw conveyor or discharge tscroll in advancingthe roll of pulp or slurry to one end of the filter drum.

As shown in Figs. 1 and 2, our discharge mechanlsm has been illustratedas applied to a conventlonal continuous rotary drum filter comprising atank I, supported at either end on pedestals 2 and 3. Mounted on thepedestals 2 and 3 respectively are bearings 4 and 4--A, in which arejournaled trunnions 5 and 6. Carried by the trunnions 5 and 6 is afilter drum 1, the periphery of which, is 'sec-.,

80 tionalized so as to form the usual filtrate compartfeatures, some ofwhich, with the foregoing, will be set forth at length in the followingdescription where that form of the invention which has been ments, eachfiltrate compartment having communication through suitable pipingextending within the drum, with an automatic valve 8 assoelated with thetrunnion 5. v

In accordance with standard practice, the pulp or slurry to be filteredis maintained at a constant level within the filter tank I, and as eachof the drum sections or filtrate compartments rotates through the bodyof pulp or slurry contained within the tank, a layer 9 of pulp or slurry(see Fig. 3) is deposited on the filter medium carried by the drum. Thisaction is brought about through an inwardly directed diiierentialfiltering pressure, which also causes the filtrate to pass through thefilter medium and out through the filtrate port ll of the automaticvalve 8. Thedrum 1 is driven through a suitable gear carried by thetrunnion 5 and housed within the gear housing l2, and which in turn isdriven by an electric motor I3 through suitable pulleys l4 and I5,

3 a speed reducer contained within a housing I], sprockets I1 and I2,belting I8 and a chain 2|. For the purpose of adjusting the cycle ofoperation of the filter, the valve 2 may be advanced or retarded througha predetermined are by means of an adjusting rod 22.

Mounted on the ends oi the tank I adjacent to the descending side of thedrum are opposed brackets 22 and 24. Journaled in bearings 25 and 22.mounted in the brackets 22 and 24, is a shaft 21, which carries adischarge roll 28 extending across theface of the filter drum I andimmediately adjacent thereto. The shaft 21 and discharge roll 22 aredriven in the same clockwise direction as the filter drum I by a chain22 operatively associated with a sprocket wheel 2 I, secured to theshaft 21, and a sprocket wheel 22 secured to the drum trunnion 2.Assuming as shown in Fig. 1 that the filter drum I rotates in aclockwise direction, the discharge roll 22 should be driven in the samedirection and at substantially the same peripheral speed. It is to benoted that although the filter drum I and the discharge roll 22 arerotating in the same clockwise direction, the adjacent peripheralsurfaces of these two members are travelling in opposed directions, andconsequently the discharge roll 28 should have positive clearance withrespect to the filter drum. The function of the roll 22, as more clearlyshown in Fig. 3, is to cause the on-coming layer or sheet 2 of solids toroll up upon itself into a cake roll 22.

Journaled in bearings 24 and 25, carried by the brackets 22 and 24, is ashaft 22 on which is mounted a double screw conveyor or dischargerscroll 21. As more clearly shown in Fig. 3, the discharger scroll 21 ismounted above the filter drum I, and to the rear of the discharge roll22, so as to define with the discharge roll 22 and the filter drum, atrough for the accommodation of the cake roll 22. The scroll 21 (seeFig. 2) is formed with a right-hand screw 22, and a lefthand screw 22,its function, as indicated in Figs. 3 and 4, being to take a cut fromthe outer portion of the cake roll 22, and to advance said out to bothends of the filter drum, where it is'discharged respectively into chutes4I and 42, supported respectively at either end of the tank I. The useof a double screw conveyor is particularly desirable in connection withrelatively long filters, although for small filters a screw conv'eyoroperating in only one direction can be eifectively used. The screwconveyor or scroll 21 is driven by a sprocket 42, keyed to the shaft 28,and operatively associated with a chain 44 and a sprocket 4S keyed tothe end of the shaft 21. The speed of rotation of the screw conveyor 31,and the pitch of the screws 22 and 29 should be so correlated that therate at which the solids are discharged is substantially equal'to therate at which these solids are formed on the filter drum.

For the purpose of aiding the discharge roll 28 in causing the initialformation of the cake roll 32, a plurality of spray nozzles 46 aremounted across the face of the filter drum I below the discharge roll28, and are so directed as to deliver a fluid current (normally water)against the on-coming cake of solids, and between the filter drum I andthe discharge roll 28. In addition to aiding the roll 28 in initiallyforming the cake roll 22, this fiuid current serves to regulate theconsistency of the cake roll 22, and also to clean the filter medium ofany solid particles that may adhere thereto.

4 r As with many other types of dischargers, the differential filteringpressure should be materially reduced or entirely eliminated adjacent tothe point at which the cake roll 22 is formed, for

otherwise the inwardly directed differential filtering pressure wouldtend to hinder the formation of thecake roll 22.

From the above description, it will be noted that in so far as theapplication of our discharger is concerned, the filter drum simplyserves as an endless support or conveyor, and that the method by whichthe solids are deposited on the endless conveyor is immaterial.

To form a cake roll 22, there should be a greater cohesive force betweenthe particles making up the cake than the adhesive force between thecake particles and the filter medium. The material of which thedischarger roll 22 is made is of no particular significance so long asit is such that there is no substantial adherence between it and thecake. Viewed in one light, the cake roll 22 may beconsidered as acontinuously formed self-couching roll, to which rotation is imparted bythe dlscharger roll 28, and the diameter of which is maintained constantby the cutting action of the screw conveyor 21.

The best application of our discharger seems t be with respect to wet.low density, fibrous cakes such as are formed during the filtration ofground wood paper making pulp.

We claim:

1. In a continuous rotary drum filter, including a filter drum mountedfor rotation on a horiaontal axis and wherein a cake is formed andcarried on the filter drum under the influence of an inwardly directeddifferential pressure; means for discharging said cake comprising: adischarge roll mounted parallel to and immediately adjacent the face ofthe filter drum on the descending side thereof for rotation in the samedirection as the rotation'of said filter drum, the

function of said discharge roll being to cause the cake carried by thedrum continuously to roll up upon itself in a direction opposite to thedirection of rotation of the filter drum along the ascending and rearface of said discharge roll; and a discharge screw mounted over andparallel to said drum and immediately adjacent to the direction assumingthe drum to be also rotating V in a clockwise direction, the function ofsaid roll being to cause said layer of solids continuously to roll upupon itself along the ascending and rearface' of said discharge roll; adischarge scroll mounted over and parallel to said drum immediatelyadjacent the rear of said discharge roll, the function of said scrollbeing continuously to advance a portion of said solids along saidscroll; and means for delivering a fluid current between said drum andsaid discharge roll in a direction generally opposed to the direction oftravel of said drum.

7 3. A device such as defined in claim 1, characterized in that thescrew is in the form of a double scroll operating to advance the cut ofsolids which it takes partly to one end of the filter drum and partly tothe other end of said drum.

.HARRY W. DmIHARD. FRANK W. BRI'I'I'AIN. ANTHONY G. SERPAS.

REFERENCES CITED The following references arebf record in the file ofthis patenjz:

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